The 5′ end group of tobacco mosaic virus RNA is m7G5′ppp5′Gp

Abstract

RNA extracted from CsCl.purified virions of tobacco mosaic virus is shown to give rise to an unusual nucleotide on digestion with RNAase T₂, in addition to the four major nucleotides. This minor component has the electrophoretic characteristics of a phosphorylated end group, but is partially resistant to bacterial alkaline phosphatase. It is, however, a substrate for venom phos-phodiesterase or nucleotide pyrophosphatase, yielding products which imply the structure m⁷G^5′ppp^5′Gp. TMV RNA, like many animal cellular and viral mRNAs recently examined, therefore has a 5′ terminus blocked by a methylated nucleotide inverted with respect to the rest of the chain.